Inter-cell interference (ICI) may be considered to be interference at a cell due to transmissions originating in another cell. Usually, ICI occurs between adjacent cells of a communications network. As an example, relatively high-powered transmissions to and from a cell edge user (CEU) operating in a first cell may cause more interference to adjacent cells utilizing the same operating frequency than relatively lower-powered transmissions to and from a cell center user (CCU) operating in the first cell to adjacent cells utilizing the same operating frequency due to correspondingly higher power levels of the transmissions to and from the CEU.
FIG. 1 illustrates a prior art communications network 100. Communications network 100 includes a first evolved NodeB (eNB) 105 and a second eNB 115. An eNB (also commonly referred to as a base station, communications controller, NodeB, and so forth) may be in communication with User Equipment (UE) operating within its coverage area. For example, eNB 105 may have a coverage area illustrated in FIG. 1 as hexagon 110, while eNB 115 may have a coverage area illustrated as hexagon 120. The coverage area of an eNB may also be commonly referred to as a cell or cells if the coverage area has been partitioned. Operating within hexagon 110 may be a first UE 125 and a second UE 130. A UE may also be commonly referred to as a mobile station, user, terminal, subscriber, wireless node, and so on.
A coverage area of an eNB (or more generally, a cell of an eNB) may be categorized based upon a distance to the eNB. For example, coverage area of eNB 105 (i.e., hexagon 110) may be categorized into two regions, with a first region being a cell center region (shown as circle 135) and a cell edge region (portions of hexagon 110 outside of circle 135, shown as region 140). Normally, with downlink fractional frequency reuse (FFR) inter-cell interference coordination (ICIC), UEs operating within a cell center region, such as UE 125, may receive transmissions made at a lower power level than UEs operating outside of a cell center region, such as UE 130, due to their closer proximity to the eNB serving the coverage area.
As indicated above, one form of ICIC is FFR ICIC. In FFR ICIC, available time and/or frequency resources (or simply resources) may be divided into multiple parts. The parts may be allocated to different transmitters. The allocation of the parts may be commonly referred to as a FFR pattern or frequency reuse pattern. Typically, in downlink transmissions, an eNB may be referred to as a transmitter, while in uplink transmissions, a UE may be referred to as a transmitter. The transmitters may then transmit only during times and/or in frequencies associated with their allocated time and/or frequency part(s), or transmit with different power densities in different time and/or frequency parts according to a predefined power density mask. Assignment of the time and/or frequency parts may be made so that adjacent and/or close transmitters cause little or no interference to one another and/or receivers. As an example, adjacent transmitters may be assigned different time and/or frequency part(s) so that their transmissions do not overlap either in time and/or frequency.
The FFR ICIC technique used may be referred by the number of parts that the available resources are divided into. As an example, FFR with Reuse-2 (or simply Reuse-2) would divide the available resources into two parts that may be assigned to transmitters in an attempt to reduce interference. Similarly, FFR with Reuse-3 (or simply Reuse-3) would divide the available resources into three parts, while FFR with reuse-1 (or simply Reuse-1) would not divide the available resources at all and may be indicative of non-FFR operation.
Soft frequency reuse (SFR) is another ICIC technique. In SFR, available resources are divided into a cell edge portion and a cell center portion. Additionally, UEs are classified as cell edge UEs (CEU) and cell center UEs (CCU). CEUs may be restricted to the cell edge portion of the resources, while the CCUs may be restricted to the cell center portion of the resources as well as lower priority access to the cell edge portion of the resources.